1. Field
This disclosure is concerned generally with the manufacture and use of pesticidal solutions and specifically with an easy-to-use pesticidal concentrate which, when dissolved in water, demonstrates excellent long term stability.
2. Prior Art
The pesticidal substance o-isopropoxyphenyl methylcarbamate is a well known insecticide and arachnidicide, the manufacture and use of which is described in U.S. Pat. No. 3,111,539 to E. Boker et al. Although the pesticide may be applied to the skin or coats of domestic animals in a variety of forms (e.g. as a powder, in a flea collar, flea stick, as a liquid, etc.), a very effective and preferred method of application involves preparing an emulsion, suspension, or solution of the pesticide which can be used to treat an animal infested with fleas, ticks, mites, and the like. Typically, such emulsions, suspensions, or solutions can be sponged or poured onto the animal or the animal can be dipped into the preparation for intimate and uniform distribution of the pesticide throughout the animal's coat.
Since the carbamate has a relatively low solubility in water, it had been a common practice to initially dissolve the carbamate in a compatible organic solvent to which a wetting agent or a surfactant is also added. In use, that concentrate was then dispersed in water to form an emulsion which was then applied to the coat of the animal. Because of objectional odors associated with the use of common organic solvents such as xylene, toluene, various naphthalenes, and kerosene, some of which may also be toxic, such solvents have been avoided where possible. Although a variety of surfactants may be used to help disperse the carbamate in an aqueous solution, the use of many surfactants results in a product which leaves an undesirable oily or sticky film on the coats of treated animals.
The carbamate has also been available as a wettable powder consisting of the active ingredient dispersed in a finely divided inert carrier to which a wetting agent and acidifying agent such as citric acid have been added. Such powders, however, tend to cause dusting and toxicity problems.
It can be appreciated that many of the above disadvantages are based primarily on the relatively low aqueous solubility of the carbamate. Even though the carbamate is pesticidally effective in relatively dilute concentrations in water (e.g. 0.125 wt.%), the direct mixing of the carbamate in water is inconvenient and time-consuming, especially in situations where only one animal is to be treated on a one-time basis. Because of this, it had become common to make the carbamate available in organic solutions or emulsion form so that the active ingredient could be conveniently diluted with water prior to use.
The above disadvantages associated with the low aqueous solubility of the carbamate and the consequent use of organic solvents and and emulsifiers have been avoided to a large extent by the recent discovery that the carbamate can be initially dissolved in a water soluble, essentially odorless, dispersion medium such as polyethylene glycol to form a conveniently storable concentrate, readily dilutable with water to form a non-oily product. One such dual solvent system is described in U.S. Pat. No. 4,048,302 to W. R. Coleman et al. The concentrate of that disclosure is prepared by dissolving about 5 to 15 weight percent of the carbamate in a compatible, non-toxic, essentially odorless, water soluble solvent such as polyethylene glycol (peg). This concentrate may be stored until needed at which time it is dissolved in about 10 to 50 parts water to form a final solution which can be applied directly to an animal's coat or into which an animal can be dipped.
Although the disclosed carbamate-polyethylene glycol concentrate provides a quick and convenient method of delivering the active ingredient into an aqueous solution to yield an essentially odorless, non-toxic, non-oily, final product, that product has a rather limited stability and must be used within a short time after preparation. Quite surprisingly, it has now been found that the stability of such products can be significantly enhanced by providing a novel pesticide concentrate, details of which are described herein.